1. Field of the Invention
The present invention relates to a coating composition for forming an anti-reflective coating layer with excellent stain resistance and anti-reflection. More specifically, the present invention provides a coating composition comprising a fluorinated silane with low surface tension, a conductive polymer with anti-static property, and a solvent.
2. Description of the Related Art
There are various display devices, including Braun tubes such as cathode ray tubes (CRTs) for monitors and color picture tubes (CPTs) for televisions; and thin film transistor-liquid crystal displays (TFT-LCDs), PDPs, RPTSs, and LCDs for cellular phones, watches, and picture display. Display devices which are exposed to natural light reflect the light, and the reflected light causes eye fatigue and headaches and lowers the contrast of the display devices by preventing images from forming clearly at an inner part of the display.
To resolve the problems, a coating layer with low reflectance has been researched. Laid-open Japanese patent publication Nos. 1997-208898 and 1996-122501 disclose a coating layer having a refractive index of 1.28–1.38 by using a silicone compound and metal fluoride such as magnesium fluoride (MgF2). European patent publication No. 0 776 925 B1 provides a coating film prepared by using a fluorinated silane and a compound including a fluorinated alkyl group, which obtains a coating film with anti-reflectance and stain-resistance by decreasing surface energy.
However, the coating layer with low reflectance including a fluorinated compound is easily charged on its surface by electrification such as through friction. Thus, dust can easily attach to the layer, and is difficult to remove. In particular, because the layer with low reflectance is usually located at an outermost part of the display, it must have resistance to stains such as from fingerprints as well as from dust. Stain-resistance of the reflective layer means that the electric charge on the surface does not disappear or stop, but flows, and thus electrostatic attraction for attaching the dust to the surface does not occur.
Therefore, the prior art has disclosed methods of preventing dust from attaching to the surface without static charge. Laid-open Japanese patent publication No. 1994-65529 disclosed conductive metal fillers such as tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), and antimony-doped zinc oxide (AZO). However, the conductive metal oxides generally have a high refractive index, thus are not expected to have an anti-reflective effect or to remove liquid-phase stains such as fingerprints.
Furthermore, in laid-open Japanese patent publication No. 2003-215306, the anti-reflection layer contains a fluorine group and a functional group with a positive charge and a negative charge so as to improve the removal of solid-phase stains such as dust and liquid-phase stains such as fingerprints. However, it is susceptible to environmental change, and has difficulty in removing the liquid-phase stains.
Therefore, it is needed to provide an anti-reflective coating composition for display devices to provide anti-reflection properties and removal properties of both liquid-phase stains and dust, by controlling the refractive index, surface energy, and conductivity of the coating layer.